Sonic method and apparatus for augmenting the flow of oil from oil bearing strata

ABSTRACT

A source of sonic vibrational energy is tightly coupled to the walls of an oil well casing, this energy source being adapted to vibrationally distort the casing in an elliptical pattern. The casing is sonically energized in this manner, the sonic energy being transferred to the surrounding oil bearing strata to induce the migration of the oil particles therein into the well. The energy source may be two pairs of piezoelectric crystals oriented on axes normal to each other, or a pair of rollers driven around the longitudinal axis of the casing.

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w MA i m e 91 l 67 BM 99 0 11 G 2 6 mU 7 M7A -5W 8 2 W M798M r d m N m nl n e pme v flm .m AFP .H HM 7 224 FOREIGN PATENTS 6/ l 960 GreatBritain..(259/Mech. Vib. Digest) Primary Examiner-Ian A. CalvertAttorney-Sokolski and Wohlgemuth ABSTRACT: A source of sonic vibrationalenergy is tightly coupled to the walls of an oil well casing, thisenergy source being adapted to vibrationally distort the casing in anelliptical pattern. The casing is sonically energized in this manner,the sonic energy being transferred to the surrounding oil bearing stratato induce the migration of the oil particles therein into the well. Theenergy source may be two pairs of piezoelectric crystals oriented onaxes normal to each other, or a pair of rollers driven around thelongitudinal axis of the casing.

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SONIC METHOD AND APPARATUS FOR AUGMENTING THE FLOW OF OIL FROM OILBEARING STRATA This invention relates to a system for sonicallyaugmenting the flow of oil from oil bearing strata, and moreparticularly to the technique and apparatus for efficiently couplingsonic energy to such strata. As described in my U.S. Pat. Nos.2,667,932; 2,680,485; 2,700,422 and 3,322,196, the oil production of awell can be substantially augmented by coupling sonic energy into thestrata surrounding the well, thereby effectively liberating theparticles of oil from the strata and causing them to migrate to thewell. This technique is particularly significant with wells that arenearing depletion where the yield can be increased by this technique soas to make further operations feasible.

In certain of the systems described in my aforementioned patents, thecoupling of the sonic energy to the strata is implemented through aliquid medium contained in the well casing. This type of fluid coupling,while having certain impedance matching advantages, has a disadvantagein that it creates undesirable back pressure impeding the flow of oil.Further, in the case of gas bearing wells, the use of liquid as thecoupling mediums is impracticable. The method and apparatus of thisinvention provides an improved technique for coupling sonic energy tothe strata without the use of a liquid coupling medium, but in which anoptimum impedance match between the energy source and the strata isachieved in a simple yet highly efficient manner. Further, by thetechnique and apparatus of this invention, the energy is transmittedinto the ground radially outwardly from the casing enabling a relativelywide energy coupling area from the vertically oriented sonic energygenerator.

It is therefore the principal object of this invention to increase theefficiency of coupling of sonic energy to petroleum bearing strata toinduce the migration of the oil particles to a well.

Other objects of this invention will become apparent as the descriptionproceeds in connection with the accompanying drawings, of which:

FIG. 1 is a cross-sectional view of a first embodiment of the device ofthe invention;

FIG. 2 is a cross-sectional view taken along the plane indicated by 2-2in FIG. 1;

FIG. 3 is a cross-sectional view of second embodiment of the device ofthe invention, and;

FIG. 4 is a cross-sectional view taken along the plane indicated by 4-4in FIG. 3.

It has been found most helpful in analyzing the technique of thisinvention to analogize the acoustically vibrating circuit utilized to anequivalent electrical circuit. This sort of approach to analysis is wellknown to those skilled in the art and is described, for example, inChapter 2 of Sonics by Hueter and Bolt, published in 1955 by John Wileyand Sons. In making such an analogy, force F is equated with electricalvoltage E, velocity of vibration u is equated with electrical current i,mechanical compliance C is equated with electrical capacitance C mass Mis equated with electrical inductance L, mechanical resistance(friction) R is equated with electrical resistance R and mechanicalimpedance Z is equated with electrical impedance 2 Thus, it can be shownthat if a member is elastically vibrated by means of an acousticalsinusoidal force F, sinwt (wbeing equal to 211' times the frequency ofvibration), that F sin wt M -1)= Where wM is equal to l/wC a resonantcondition exists, and the effective mechanical impedance Z,,," is equalto the mechanical resistance R,,,, the reactive impedance components wMand 1 /mC,, cancelling each other out. Under such a resonant condition,velocity of vibration u is at a maximum, power factor is unity, andenergy is more efficiently delivered to a load to which the resonantsystem may be coupled.

It is important to note the significance of the attainment of highacoustical Q in the resonant system being driven, to increase theefficiency of the vibration thereof and to provide a maximum amount ofpower. As for an equivalent electrical circuit, the Q of an acousticallyvibrating circuit is defined as the sharpness of resonance thereof andis indicative of the ratio of an energy stored in each vibration cycleto the energy used in each such cycle. Q is mathematically equated tothe ratio between mM and R,,,. Thus, the effective Q of the vibratingcircuit can be maximized to make for highly efficient, high-amplitudevibration by minimizing the effect of friction in the circuit and/ormaximizing the effect of mass in such circurt.

In considering the significance of the parameters described inconnection with equation (I), it should be kept in mind that the totaleffective resistance, mass, and compliance in the acoustically vibratingcircuit are represented in the equation and that these parameters may bedistributed throughout the system rather than being lumped in any onecomponent or portion thereof.

It is also to be noted that orbiting-mass oscillators may be utilized inthe implementation of the invention that automatically adjust theiroutput frequency and phase to maintain resonance with changes in thecharacteristics of the load. Thus, in the face of changes in theeffective mass and compliance presented by the load with changes in theconditions of the work material as it is sonically excited, the systemautomatically is maintained in optimum resonant operation by virtue ofthe lock-in characteristic of applicants unique orbiting-massoscillators. Furthermore in this connection the orbiting-mass oscillatorautomatically changes not only its frequency but its phase angle andtherefore its power factor with changes in the resistive impedance load,to assure optimum efficiency of operation at all times.

Briefly described, the technique and apparatus of the invention involvesthe utilization of a sonic energy source, the output of which is tightlycoupled to the walls of a well casing which has been sunk into oilbearing strata. The sonic energy source, which in one embodimentcomprises two pairs of piezoelectric crystal transducers, and in anotherembodiment a pair of mechanically driven roller members, vibrationallydistort the casing wall in an elliptical pattern in directions normal tothe longitudinal axis thereof. This cyclical vibration distortion of thecasing results in the transfer of sonic energy radially outwardly fromthe casing walls into the strata, there being a highly efficientimpedance match between the high impedance sonic generator output andthe high impedance load formed by the casing and the earthen materialagainst which it abuts.

In the embodiment utilizing the two pairs of piezoelectric crystaltransducers, one pair of such transducers is oriented along an axisnormal to that along which the other pair is oriented, all of suchtransducers being of an elongated configuration with their longitudinalaxes oriented substantially parallel to the longitudinal axis of thecasing. The transducers are coupled tightly to the casing wall and thefirst transducer pair is excited in phase opposition to the second suchthat while one is in an outward expansion cycle portion, the other ismoving inwardly, thereby resulting in the desired elliptical vibrationalpattern.

In a second embodiment the same end result is achieved by means of apair of roller members positioned opposite each other with theirlongitudinal axes substantially parallel to the longitudinal axis ofcasing, these rollers being rotated together to provide thedesiredelliptical vibrational pattern.

Referring now to FIGS. 1 and 2, a first embodiment of the device of theinvention is illustrated. Casing member 11 is an oil well casing membersunk into strata 12 in normal fashion and has the usual perforations 14formed therein to permit oil from the surrounding strata to enter thecasing. Casing 11 is generally of a thin wall steel which can readily beelliptically distorted in response to the elliptical vibration patternset up by the vibration generator.

The vibration generator is formed by a first pair of piezoelectriccrystal transducers a and 15b, oriented opposite each other along afirst transverse axis, and a second pair of similar transducers 16a and16b oriented opposite each other along a second transverse axis normalto the first axis. Transducers 15a, 15b, 16a and 16b may be fabricatedof a piezoelectric material such as barium titanate. The transducermembers are elongated in form and are oriented so that theirlongitudinal axes are substantially parallel to the longitudinal axis ofeasing member 11. Transducers 15a, 15b, 16a and 16b are clamped betweentubing string 18 and wedge-shaped clamp members by means of bolts 21.Clamp members 20 and transducers 15a, 15b, 16a and 16b are thus attachedto tubing string 18 to form an integrated unit.

The clamping members 20 are tightly coupled to the inner wall of casing11 by means of wedge-shaped slip member in the following manner: Thetubing string 18 with the transducers 15a, 15b, 16a and 16b and clampmembers 20 attached thereto, by means of bolts 21, is first carefullylowered into casing 11 with the slip members 25 suspended from the topedge of clamp members 20 on their rim portions 25a. The dimensions ofthe various elements involved must of course be such as to permit theeasy passage of this assembly down into the casing. Care must also betaken in lowering these members to avoid any accelerations which mightcause the clamp members 20 to slip downwardly relative to slip member25. When the portion of casing 11 has been reached at which it isdesired that acoustical energy be coupled to the strata, the units maybe seated in position at this location by allowing the tubing string l8to drop suddenly, this downward acceleration causing the clamp members20 to move downwardly relative to slip members 25. By virtue of thewedge action between the clamps and the slip members, the serratedportions 25b of the slip members are caused to tightly grip the innerwalls of the casing, the walls of clamp members 20 tightly engaging theslip members by virtue of this wedging action.

Crystal transducers 15a, 15b, 16a and 16b are vibrationally energized bymeans of an oscillating electrical signal fed thereto by means of cables35, the frequency of such excitation being in the sonic range, i.e.,typically of the order of 10,000 cycles. To achieve the desiredelliptical distortion in an optimum manner, transducers 15a and 15b areexcited with signals that are in phase opposition to those utilized forexciting transducers 16a and 16b, i.e., the signals fed to transducers15a and 15b are 180 out of phase with those fed to transducers 16a and16b. This results in a cyclical elliptical vibrational pattern whichcyclically deforms flexible casing 11 as indicated by dotted lines 40and 41 in FIG. 2. Thus, during the portions of the vibrational cyclewhen transducers 15a and 15b are in the portions of their vibrationalcycle which involve an outward displacement, such as to deform thecasing as indicated by dotted line 40, transducers 16a and 161) are inthe portion of their vibrational cycle involving an inward displacement.Conversely, during the opposite halves of the vibrational cycle of thetransducers when transducers 16a and lob are experiencing an outwarddisplacement, the casing is deformed as indicated by dotted lines 41.Thus, the two pairs of transducers operate cooperatively to cause thedesired elliptical vibration pattern, this vibrational energy beingtransmitted radially outwardly into the strata 12 from the walls of thecasing.

The vibrational energy, it is to be noted, is transmitted substantiallyuniformly to the casing along the entire longitudinal extent of thetransducers, thus providing a fairly wide radiation area which includesthe entire extent of the casing wall which corresponds to thelongitudinal extent of the transducers. It is also to be noted that thistype of vibrational pattern involves a maximum transfer of energyradially outwardly from the casing wall with a minimal transmissioneither up or down the tubing string and casing, thus minimizing theinefficient dissipation of the energy along these elements.

As already noted, for optimum efi'iciency, it is highly desirably toadjust the frequency at which the transducers are excited to one atwhich resonant vibration of the crystal, the mounting structure and thecasing in the desired elliptical vibration mode is attained.

Referring now to FIGS. 3 and 4, a second embodiment of the device of theinvention is illustrated. In this embodiment, the elliptical vibrationalpattern is generated by a mechanical oscillator rather than through anelectrical transducer, typically at lower frequency, but otherwise thesame general operational results are achieved. Tubing string 18 hasclamp members 20 attached thereto by welding and is inserted into casing11 with slip members 25 suspended therefrom and clamped to the innerwall thereof at a desired location in the same manner as described forthe first embodiment by means of the wedge-shaped slip members 25.Contained within tubing string 18 which is fabricated of an elasticmaterial such as steel is an orbiting mass oscillator having rollermembers 46 and 47 which are oriented opposite each other and arerotatably driven around a raceway formed by the inner walls of tubingstring 18. Drive shaft 45 is supported for rotation in sleeve bearing 50formed in the bottom of the casing string and is rotatably driven by amotor (not shown) at a speed which determines the vibration frequency ofthe elliptical vibration pattern, typically 60-400 c.p.s. Fixedlyattached to shaft 45 are drive arms 51 and 52. These drive arms extendoutwardly from the shaft and have elongated slot portions 51a and 52awhich engage pin portions 46a and 470 which extend from the ends of therollers.

Thus, a shaft 45 is rotated, rollers 46 and 47 are rotatably drivenabout the raceway formed by the inner wall of the tubing string. Thisresults in a cyclical elliptical deformation of tubing string 18 asindicated by dotted lines 60, this deformation causing a likedeformation of casing 11 as indicated by dotted pattern 62. Thisdeformation pattern of course will follow the rotation of rollers 46 and47 in a cyclical fashion in response to the outward force imparted tothe portions of the tubing string wall against which the rollers abut asthey rotate. As noted for the first embodiment, the rotation speed ofrollers 46 and 47 is preferably adjusted for optimum resonant vibrationat a low frequency mode of the vibration system including the tubingstring and casing. The vibrational energy is radiated outwardly into thestrata along the entire longitudinal extent of the roller members in thesame manner as described for the first embodiment.

It is to be noted that the elliptical distortion of the casing producedby the technique of the invention results in an elastic motion of suchcasing without the center of gravity of the casing moving. That is tosay, the casing is not being shaken sideways in a totally bodilymovement as, for example, in situations where a single roller is rotatedaround the inside of a casing to loosen it from its anchored position.

The apparatus and technique of this invention thus enable the highlyefficient coupling of sonic energy to the strata surrounding a wellcasing to engender the separation of oil particles from such strata andto cause the migration of such particles to the well. This end result isachieved by the direct coupling of a high impedance sonic energy sourceto the high impedance load formed by the strata, this end result beingachieved by directly sonically energizing the casing in an ellipticalvibration mode, such vibration being transmitted radially outwardly fromthe walls of the casing.

I claim:

I. A method for coupling vibrational energy to oil bearing strata toenhance the removal of oil therefrom comprising the steps of:

placing an oil well casing into said strata,

tightly coupling a first and second pair of electroacoustic transducersto the inner walls of said casing in the region of the oil bearingstrata, the transducers of each pair being coupled to opposite walls ofthe casing, with the first pair being oriented normal to the secondpair, and vibrationally energizing said transducers in a manner such asto cause elastic vibrational deformation of the casing radiallyoutwardly in directions substantially normal to the longitudinal axis ofthe casing, said first pair of transducers being vibrationally excitedin phase opposition to the excitation of said second pair.

2. A method for coupling vibrational energy to oil bearing strata toenhance the removal of oil therefrom comprising the steps of:

placing an oil well casing into said strata,

tightly coupling a pair of roller members to the inner walls of saidcasing in the region of the oil bearing strata, said roller membersbeing oppositely oriented with respect to the longitudinal axis of thecasing and with their longitudinal axes substantially parallel thereto,and

rotationally driving said roller members to provide an ellipticalcyclical force pattern against the wall of the casing such as to causeelastic vibrational deformation of the casing radially outwardly indirections substantially normal to the longitudinal axis thereof.

3. Apparatus for sonically energizing oil bearing strata to induce theflow of oil therefrom comprising:

a casing member sunk in said strata,

a tubing string member,

first and second pairs of piezoelectric crystal transducers attached tothe outer wall of said tubing string member with the transducers of eachpair oppositely oriented with respect to the longitudinal axis of thetubing string member, said first and second pair of transducers beingoriented in mutually orthogonal relationship,

means for clamping said transducers to the inner wall of said casing,thereby tightly coupling said tubing string to said casing in thevicinity of the oil bearing strata, and

means for energizing said crystal transducers so as to cause cyclicalradial deformation of the walls of the casing in an elliptical patternin directions substantially normal to the longitudinal axis of thecasing, in the region of the oil bearing strata. v

4, The apparatus of claim 3 wherein said first pair of transducers issonically energized in phase opposition to said second pair oftransducers.

5. The apparatus of claim 4 wherein said transducers are elongated, thelongitudinal dimension thereof being oriented substantially parallel tothe wall of said casing so as to provide a substantially uniform radialdeformation force along the extent of said casing corresponding to theextent of said transducers.

6. Apparatus for sonically energizing oil bearing strata to induce theflow of oil therefrom comprising:

a casing member sunk in said strata,

a tubing string member,

a pair of roller members oppositely oriented with respect to thelongitudinal axis of the casing with their longitudinal axessubstantially parallel thereto, said roller members being adapted to berotationally driven around a raceway formed by the inner walls of saidtubing string member,

means for tightly coupling said tubing string member to said casing inthe vicinity of said oil bearing strata, and

means for driving said roller members around said raceway so as to causecyclical radial deformation of the walls of said casing in an ellipticalpattern in directions substantially normal to the longitudinal axis ofthe casing in the region of the oil bearing strata.

2. A method for coupling vibrational energy to oil bearing strata toenhance the removal of oil therefrom comprising the steps of: placing anoil well casing into said strata, tightly coupling a pair of rollermembers to the inner walls of said casing in the region of the oilbearing strata, said roller members being oppositely oriented withrespect to the longitudinal axis of the casing and with theirlongitudinal axes substantially parallel thereto, and rotationallydriving said roller members to provide an elliptical cyclical forcepattern against the wall of the casing such as to cause elasticvibrational deformation of the casing radially outwardly in directionssubstantially normal to the longitudinal axis thereof.
 3. Apparatus forsonically energizing oil bearing strata to induce the flow of oiltherefrom comprising: a casing member sunk in said strata, a tubingstring member, first and second pairs of piezoelectric crystaltransducers attached to the outer wall of said tubing string member withthe transducers of each pair oppositely oriented with respect to thelongitudinal axis of the tubing string member, said first and secondpair of transducers being oriented in mutually orthogonal relationship,means for clamping said transducers to the inner wall of said casing,thereby tightly coupling said tubing string to said casing in thevicinity of the oil bearing strata, and means for Energizing saidcrystal transducers so as to cause cyclical radial deformation of thewalls of the casing in an elliptical pattern in directions substantiallynormal to the longitudinal axis of the casing, in the region of the oilbearing strata.
 4. The apparatus of claim 3 wherein said first pair oftransducers is sonically energized in phase opposition to said secondpair of transducers.
 5. The apparatus of claim 4 wherein saidtransducers are elongated, the longitudinal dimension thereof beingoriented substantially parallel to the wall of said casing so as toprovide a substantially uniform radial deformation force along theextent of said casing corresponding to the extent of said transducers.6. Apparatus for sonically energizing oil bearing strata to induce theflow of oil therefrom comprising: a casing member sunk in said strata, atubing string member, a pair of roller members oppositely oriented withrespect to the longitudinal axis of the casing with their longitudinalaxes substantially parallel thereto, said roller members being adaptedto be rotationally driven around a raceway formed by the inner walls ofsaid tubing string member, means for tightly coupling said tubing stringmember to said casing in the vicinity of said oil bearing strata, andmeans for driving said roller members around said raceway so as to causecyclical radial deformation of the walls of said casing in an ellipticalpattern in directions substantially normal to the longitudinal axis ofthe casing in the region of the oil bearing strata.